22 Mr Scott's Description of 



in diameter, exclusive of the projecting parts. The spiral groov- 

 ed pattern was one inch and three quarters in thickness, and 

 the plain pattern one inch and a quarter thick, as also were 

 the projecting parts of both patterns. The spiral groove was 

 cut half an inch in depth, half an inch wide at bottom, and 

 seven-eighths of an inch at top. The ridge between the grooves 

 was left half an inch in breadth at top, and seven-eighths of an 

 inch at bottom. From these two patterns iron casts were taken. 

 The faces of both these cast-iron plates were made truly flat, 

 and a very small chiseled groove was cut along the middle of 

 the ridge between the grooves, and a corresponding chiseled 

 groove was cut in the inch and quarter thick plate. These 

 two plates were then cemented together by means of well-pre- 

 pared iron cement, part of it filling the chiseled grooves in 

 both plates ; the projecting parts a, 6, c, d, e, /, g, h, Figs. 

 1 and 2, were bolted together by screw bolts, five-eighths of 

 an inch square, made of the best iron ; in all fifteen bolts, as 

 marked by the small square bolt holes in Figs. 1 and 2; 

 the projecting parts of Fig. 1 being all, except that marked 

 h, one and a quarter of an inch in thickness, which leaves a 

 space of half an inch between the projecting parts of the two 

 plates, for the more effectually screwing the plates close to- 

 gether. These two plates when thus joined form only the 

 one-half of the generator, as there is another half almost in 

 every respect similar to be placed perpendicularly over the 

 one described ; having a strong cast-iron pillar with flanges, 

 as represented by Fig. 3, placed in the centre between the 

 halves : These flanges are strongly secured by four screw bolts 

 to each of the halves of the generator. The centre pillar is 

 twelve inches in height and four and a half inches in diameter, 

 with a bore up its centre of one inch and a quarter in diameter. 



Fig. 4 represents a section of the generator answering to 

 the description already given, placed in a furnace, of which a 

 section is also given. 



The generator is supported in the furnace by cast-iron 

 brackets represented by Fig. 5 and 6, built into the sides 

 of the furnace for the projecting parts of the generator to rest 

 on, where F, Fig. 4, is the Are place, A the ash pit, and C 

 part of the chimney. R represents part of the pipe that leads 



